bedework

Bedework is an open-source enterprise calendar system that supports public, personal, and group calendaring. It is designed to conform to current calendaring standards (iCalendar RFC 2445 iCal, iTIP: RFC 2446, CalDAV: RFC 4791, VVENUE) with a goal of
attaining strong interoperability between other calendaring systems and clients (Mozilla Lightning, Apple iCal). Bedework is built with an emphasis on higher education, though it is used by many commercial
enterprises. You may choose to deploy Bedework for public events calendaring, personal calendaring and
scheduling, or both. It is suitable for embedding in other applications or in portals and has been deployed across a wide range of environments.